Review Table 1, Characteristics of Apes and Humans. Gibbons, chimpanzees,
gorillas, and orangutans are four groups included in the ape family. Chimpanzees
and gorillas represent the African side of the family; gibbons and orangutans
represent the Asian side of the family. We focus only on the chimpanzee and
gorilla in this activity. The only modern representative of the human family is
Homo sapiens, although paleontologists have found fossil remains of other
members, such as Australopithecus afarensis ("Lucy") and Homo sapiens
neandertalensis.
Table 1.
Characteristics of Apes and Humans
Characteristics Apes
Posture
Bent over or quadrupedal
Humans
Upright or bipedal
"knuckle-walking" common
Leg and arm
length
Arms longer than legs; arms adapted Legs usually longer than arms;
for swinging, usually among trees
legs adapted for striding
Feet
Low arches; opposable big toes,
capable of grasping
High arches; big toes in line
with other toes; adapted for
walking
Teeth
Prominent teeth; large gaps between
canines and nearby teeth
Reduced teeth; gaps reduced or
absent
Skull
Bent forward from spinal column;
rugged surface; prominent brow
ridges
Held upright on spinal column;
smooth surface
Face
Sloping; jaws jut out; wide nasal
opening
Vertical profile; distinct chin;
narrow nasal opening
Brain size
80 to 705 cm3 (living species)
2400 to 2000 cm3 (fossil to
present)
Age at puberty
Usually 10 to 13 years
Usually 13 years or older
Breeding season Estrus at various times
Continual
In this activity, you need to use this data to determine the relationships between humans,
apes, and other animals. It might not be obvious that closely related organisms share
more similarities than do distantly related organisms. Structures might be similar
because they carry out the same functions or because they were inherited from a common
ancestor. Only those similarities that arise from a common ancestor can be used to
determine evolutionary relationships.
Diagrams called branching trees
illustrate relationships among
organisms. One type of branching
tree, called a morphological tree, is
based on comparisons of skulls, jaws,
skeletons, and other structures. Look
carefully at the morphological tree.
Find the part of the morphological
tree that shows the relationships
Evolutionary relationships among organisms
derived from comparisons of skeletons and
other characteristics.
between gorillas, chimpanzees, and
humans. Notice that there are no
lines showing these relationships. Work with partners to develop three
hypotheses to explain how these organisms are related. On a sheet of notebook
paper, make 3 diagrams of you hypotheses by drawing lines from Point A to each
of the three organisms (G = gorilla, C = chimpanzee, H = human, A = common
ancestor).
Now look at the 4 strands of “dna” (paperclips) provided at your station. Notice
how they are labeled and that each different color of paper clip represents one of
the four bases of DNA:
black = adenine(A) green = guanine(G) white = thymine(T) red = cytosine (C)
Compare the human DNA to the chimpanzee DNA by matching the strands base
by base (paper clip by paper clip). Count the number of bases that are not the
same and record the data in your data table. Repeat these steps with the human
DNA and the gorilla DNA.
Data Worksheet
3 Hypothetical Morphological Trees:
 Hybridization data for human DNA
Human DNA compared to:
Chimpanzee DNA
Number of matches
Unmatched bases
Gorilla DNA
Data for common ancestor DNA
Common ancestor DNA compared to:
Number of matches
Unmatched bases
Human DNA
Chimpanzee DNA
Gorilla DNA
Using all your data, answer the following questions:
1. How do the gorilla DNA and the chimpanzee DNA compare with the
human DNA?
2. What do these data suggest about the relationship between humans,
gorillas, and chimpanzees?
3. Does your data support any of your hypotheses? Why or why not?
4. Which DNA is most similar to the common-ancestor DNA?
5. A comparison of many more DNA sequences indicates that human DNA
and chimpanzee DNA are 98.8 percent identical. What parts of your data
support this result? Based on the hypothesis that your data best supported,
which of the following statements is most accurate? Explain your answer in a
short paragraph.
(a) Humans and apes have a common ancestor.
(b) Humans evolved from apes.
Prep Key & Answer Key
Possible evolutionary relationships:
DNA Chains:
Position 20
 Position 1
A-G-G-C-A-T-A-A-A-C-C-A-A-C-C-G-A-T-T-A
Label this strand "human DNA." This strand represents a small section of the
gene that codes for human hemoglobin protein.
Position 20
 Position 1
A-G-G-C-C-C-C-T-T-C-C-A-A-C-C-G-A-T-T-A
Label this strand "chimpanzee DNA." This strand represents a small section of
the gene that codes for chimpanzee hemoglobin protein.
Position 20
 Position 1
A-G-G-C-C-C-C-T-T-C-C-A-A-C-C-A-G-G-C-C
Label this strand "gorilla DNA." This strand represents a small section of the
gene that codes for gorilla hemoglobin protein.
Position 20
 Position 1
A-G-G-C-C-G-G-C-T-C-C-A-A-C-C-A-G-G-C-C
Label this strand "common ancestor DNA." This DNA strand represents a small
section of the gene that codes for the hemoglobin protein of a common ancestor
of the gorilla, chimpanzee, and human.
Answers to Data Table:
The data for the hybridizations are as follows: chimpanzee DNA, 5 unmatched
bases; gorilla DNA, 10 unmatched bases.
The data for the common ancestor is: human DNA, 10 unmatched bases;
chimpanzee DNA, 8 unmatched bases, and gorilla DNA, 3 unmatched bases.
Question Answers:
1. The human DNA is more similar to the chimpanzee DNA than the gorilla DNA.
2. The data suggest that humans are more closely related to the chimpanzee
than they are to the gorilla.
3. The data lend support to the hypothesis that the chimpanzee is more closely
related to humans than the gorilla is.
4. Gorilla DNA is most similar to the common-ancestor DNA.
5. The students should infer that humans and apes share a common ancestor,
represented by a common branching point.